Nitrocellulose composition



Patented F eb. 26, 1929.

UNITED STATES 1,703,415, PATENT OFFICE.

HAMILTON BRADSHAW, OF WILMINGTON, DELAWARE; EDGAR I-I. NOIJJAU, 01E

NEWBURGH, NEW YORK; AND BICHA BD G. WOODBRIDGE, OF WILMINGTON, DELA- WARE, ASSIGNORS T0 E. I. DU FONT DE NEMOURS & COMPANY, OF WILMINGTON, DELAWARE, CORPORATION OF. DELAWARE.

NITROCELL'ULOSE COMPOSITIQN.

Ndfirawing. Applicationnled December 21, 1921, Serial No. 523,991. Renewed March 21, 1924.

by a special treatment hereinafter described.

Une object of our invention is to utilize pyro nitrocellulose in the manufacture of artificial leather of the coated fabric type, in coating compositions intended for the coating of paper, fabrics, and split leathers, and in eneral for leather substitute uses.

Knother object of our inventionis to uti-,

lize pyro nitrocellulose in the manufacture of solutions such as lacquers, bronzing liquids, etc. for the coating of metal, Wood, and other surfaces.

By pyro nitrocellulose is meant that grade of nitrocellulose soluble in a mixture of 2 parts by volume of ether to one part of ethyl alcohol and havinga nitrogen content of about 12.60%. A specific example of this grade of nitrocellulose is a product having asolubility in ether-alcohol mixture ofabove 95%, generally above 99%, and a nitrogen content of 12.50 to 12.70% such a product is commonly known as pyro and is hereinafter referred to as such.

Large quantities of pyro nitrocellulose remained unused after the cessation of the W'orld War. Attempts to use the pyroin dope solutions intended for the coating of fabrics showed that it difiered from the regular type of pyroxylin used by the pyroxylin industry not only in having a higher nitrogen content but 1n possessing high viscosity,

inferior solubility in the customary solvents,

inferior ailinity for caster, and other v etable oils, and in general poorerqualities or film making purposes. Of the inferior quali ties, those of high viscosity and low solubility in methyl and ethyl alcohol are not dificult to recognize even by those less skilled in the ties for use for coating purposes. For examart. The reduction in the viscosity of the pyro by boiling in water did not give to the resulting boiled material the desired qualiple, artificial leather made from pyro previously boiled to reduce its viscosity appeared visually to'be satisfactory and might have been accepted as such by one not skilled in the art. However, the pyro-castor oil film exhib-' ited a tendency to softness which peculiar Weakness grew more and more pronounced When the artificial leather Was stored at atmospheric or higher temperature, the film becoming soft and mushy.

, Wordens lechnology of Cellulose Esters, vol. 1, part 3, page 1691 states-From 11.5% 12970 N, are included the class of pyroxyl1ns loosely defined and with no clearcut lines of analytical demarcation, but including the nitrocellulose employed in artificial leather, lacquers, waterproofing solution, bronzing liquids, nitro-artificial filaments and the enameling and coating of hides and splits. I The pyroxylins are produced in an endless number of grades for specific purposes, where the solubility, flow, adhe-l sion, ability to mix with oils, tensile strength and other factors are modified and manipulated in the process of nitration without at the same time var ing but little the nitrogen content of the nished product.

The above statements by Worden are rather confirmatory of our resultsand indicate that the desirable limits of nitrogencontent for pyroxylin for use in the artificial leather industry and for coating purposes in general have by experience been found to be much lower than the nitrogen content of that grade of nitrocellulose designated as pyro.

We have discovered that by subjecting the pyro to a precolloiding treatment, in the presence of diphenylamine, with a solvent mixture composed, for example, of approximately 2 partsether by volume to]. part denatured ethyl alcohol followed by a seasoning treatment at a temperature of, say, between and C. for about 15 to 25 days, that it gives coated products possessing superior qualities to those given by the pyro witht ll out previous precolloiding with ether-alcoto which we may subject the pyro before us- 7 mg it for coating purposes may difier con of the weight given above.

siderably in detail but we prefer to use a treatment substantially as follows: '2

We first dehydrate the pyro containing about 35% of water by forming it into blocks containingabout 40 pounds dry weight. This we do by means of an hydraulic press. We then pump about 50 pounds of denatured ethyl alcohol (formula containing gallon benzene per 100 gallons of alcohol) through the pyro, thus displacing the water. We remove the excess of alcohol by'squeezing the I block of material under high pressure until it weighs about 53 pounds and contains about 13%, pounds alcohol and 40 pounds pyro (dry weight). After breaking up the block of alcoholized pyro by mechanical means, we place same in a mixer provided with brine refrigeration and colloid it inthe presence of about 0.5% of diphenylamine based on the dry weight of the pyro by the addition of about 26% pounds of" ether, in which the diphenylamine is previously dissolved, for each block of dehydrated pyro After mixing for not more than one hour for the purpose of thoroughly colloiding the pyro and thoroughly distributing the diphenylamine throughout the-colloided mass, we reduce the colloid to a form convenient for subsequent handling by shaping it intoblocks,.then, by means of an hydraulic press, extruding the colloid through suitable perforations, and finally granulating the-extruded material on a cutting machine into grains of suitable size.

These grains may, forexample, be small cylinders about 0.4 of an inch long and about 0.2

of an inch in diameter, preferably provided with about 7 evenly spaced, longitudmal perforations each about 0.02 of an inch in diameter for facilitating escape and recovery of solvent.

The bulk of ether-alcohol solvent may be re- ,moved from the grains of seasoning, if desired, in a suitable solvent recovery apparatus at a temperature of about 6., the solvent which vaporizes being condensed. The colloided grains, which have been thus treated to recover the solvent, are then fur-,

ther seasonedby heating in hot water for about 15 to 25 days at a temperature of about 60 C, afterwhich the colloided grains are air dried at a temperature of about 60 C. until the moisture in the colloid is reduced to about 1.0 to 2.0%. The colloided grains are I then stored in air-tight receptacles for a still further seasoning treatment at atmospheric temperature, which treatment may extend over a period of many months, (usually more than 4 months), until the viscosity of a standard testing solution of the colloided grains is reduced to 200 seconds or below when measured by the procedure hereinafter described.

We have found that the pyro precolloided and seasoned as above described does not give coatings, i. e., films, with the tendency to soften and become mushy onstorage which is characteristic of pyro which has been boiled to reduce its viscosity, but instead gives coatings of satisfactory toughness which retain this quality during storage for a considerable period of time. In fact experiments show that the degree of deterioration'of the new coatings or films up ageing, due to the gradual and inevitabl degradation of the nitrocellulose, is even less than the deterioration which occurs in coatingsmade according to the present day standard methods from nitrocellulose having less than 12% nitrogen.

The improved quality-for-coating purposes of the pyro whichhas been precolloided and seasoned substantially as above described, is to be attributed to a number of factors. Of these, the most readily measured is the very gradual change in the viscosity characteristic which occurs during the seasoning process,

which we believe tends to bring the viscosity characteristics of all component parts of the colloid to the same point. For example, a standard testing solution of a sample of pyro before precollo1ding gave a viscosity of 850 seconds at 28 C. by the so-called steel ball method, the time being that required for a steel ball to fall in a 1.25 tube through 10" of the'standard testing solution, which solution is made by dissolving 16 ounces of the pyro in a gallon of solvent mixture composed of benzene 50 parts, denaturedoethyl alcohol 25 parts, and ethyl acetate 25 parts. After precolloiding with ether-alcohol mixture and seasoning for about 20 days at a temperature of 60 (1,4 days of which were in solvent recovery apparatus for the purpose of recovering the ether and alcohol, and 15 days of which were in hot water at 60 (1., the remaining day being in air, the viscosity of the colloid was reduced to about 400 seeonds. Further seasoning of the colloid for 35 months at atmospheric temperature gradually reduced'the viscosity of the colloid to about 85 seconds. A seasoning treatment at atmospheric temperature for about 20 months will ordinarily effect a satisfactory reduction in viscosity.

An important feature of our invention is thatthe diphenylamine presen in the pyro advantage in retarding the'development of rancidity.

To prepare compositionssiiitable for coating fabrics we mix with the precolloided pyro a softener which may be either a non-solvent softener such as a non-drying vegetable oil (e. g. castor oil) or a 'solvent'softener such as dibutyl phthalate, or preferably both.

' These compositions are of course applied to the fabric in the form of their solutions, the volatile solvent consisting usually of an active solvent and a diluent.

Typical coatings or films made from the precolloided pyro may have, for example, the following compositions:

Parts by weight. Per cent. L- Precolloided pyro 1. oo 30. 8 -26. 70

- Castor oil--. 1. 63-2. 56.

Pigmen II. Precolloided pyro Blown rapeseed oil Pigment III. Precolloigied pyro The above compositions represent the nonvolatile portion of the solutions from which the coatings or films are produced.

As the volatile solvent there may be used for example a mixture of 50 parts benzene,

- modifications,

25 parts ethyl acetate, and 25 parts denatured alcohol. From 7 to 8 parts of this solvent mixture maybe uesd to 1 part of the nonvolatile composition of any'of the above examples to form the coating solution. The

, pigment must of course be ground in a poracetone (a commercial mixture containing methyl acetate, methyl alcohol, and acetone), or an ether-alcohol mixture; and as the diluent there may be used, for example, ethyl alcohol, benzine or benzol.

It will of course be understood that various not specifically described above, may be made in our new process and product without departing from our invention.

We claim 1. A coating composition consisting essen tially of precolloided and seasoned pyro nitrocelluloseand a softener therefor.

2. A coating composition consisting essentially of precolloided and seasoned pyro nitrocellulose and a softener therefor comprising a non-drying vegetable oil.

3. A coating composition consisting essentially of precolloided and seasoned pyro nitrocellulose and a softener therefor comprising a non-drying vegetable oil and a solvent softener.

4. A coating composition comprising ni- 'trocellulose offrom 12.5 to 12.7% nitrogen content, diphenylamine, a. vegetable oil, and dibutyl phthalate. 7

5. The process of making a coating composition which comprises colloiding a nitrocellulose of more than 12.4% nitrogen content, comminuting the resulting colloid, seasoning the comminuted mass for from about 2 to 4 weeks at a temperature of about 0., further seasoning the mass at about atmospheric temperature until a standard testing solution made therefrom shows a viscosity of less than 200 seconds when measured'by the method hereinbefore described, and then dissolving the seasoned comminuted mass in a nitrocellulose solvent. I

6. The process of making a coating composition which comprises dissolving in a nitrocellulose solvent a nitrocellulose mass obtainable by colloiding a nitrocellulose of more than 12.4 nitrogen content, comminutin the resulting colloid, seasoning the comminuted mass for from about 2 to 4 weeks at a temperature of about 60 0., further seasoning the mass at about atmospheric temperature until a standard testing solution made therefrom shows a viscosity of less than 200 seconds when measured by the method hereinbefore described.

7. The process of making a coating composition which comprises colloiding :1. nitro-' cellulose of from about 12.4 to 12.7% nitrogen content, comminuting the resulting colloid, seasoning the comminuted mass partly at an elevated temperature, until a standard testing solution made therefrom shows a viscosity of less than 200 seconds when measured by the method'hereinbefore described, and then dissolving the seasoned, comminuted mass in a nitrocellulose solvent.

8. A coating composition comprising a recolloided and seasoned nitrocellulose havmgza. nitrogen content of from about 12.4 to 12. a vegetable oil, and dibutyl phthalate.

9. A coating composition comprising a precolloided and seasoned nitrocellulose having a nitrogen content of from about 12.4 to 12.7%, a non-solvent softener, and a neutral phthalate.

In testimony whereof we afiix our signatures.

HAMILTON BRADSHAW. EDGAR HZ. NOLLAU. RICHARD e. WOODBRIDGE. 

